Acute infant pain remains undertreated due to lack of valid and reliable measures of infant pain, which, in turn, have resulted from insufficient knowledge concerning valid indicators of pain in infants. Research in Years 01-05 discovered several infant behaviors that are altered in response to pain and produced a scientifically-based model of infant pain assessment. The purposes of the proposed research seeks to improve nursing assessments of acute infant pain by testing the model derived from Years 01-15 and developing and testing a clinical tool with age-appropriate subsections for assessing infant pain based upon this model. The five aims for pursuing these purposes are: (1) to test the infant pain assessment model developed during Years 01-05; (2) to subsequently construct a clinical assessment tool (which has alternative age-appropriate subsections for 0.5-6 month old and 7-12 month old infants) that reflects the assessment process; (3) to estimate criterion-like validity of the tool. The model will be tested (Aim 1) by correlating objectively measured infant behaviors (including cry features) with assessed level of pain as determined by a panel of expert pediatric nurses for 48 0.5 to 12 month old infants. Elements in the model will be confirmed if > 3 behaviors representing each element correlate > .55 with level of pain. Construction of a clinically useful tool will involve consultation with and pilot testing by both experienced nurses and more clinically naive nursing students. Correlations of the assessed pain levels of 36 videotaped infants, between expert pediatric nurses and pediatric nursing students, will provide estimates of criterion-like validity of the tool (Aim 3). Correlations between the nursing students' assessed pain levels of these 36 videotaped infants at two different points in time will provide a quantitative estimate of clinical usefulness. In addition, the volunteers will provide "on-the-job" feedback on the usefulness of the tool in each clinical setting.